1. Field of the Invention
The present invention relates to a recording/reproducing apparatus and method for digitally recording and reproducing a television signal.
2. Description of the Related Art
PAL plus and EDTV-2
Television signals are encoded using accepted encoding standards. The United States adopted the NTSC (National Television System Committee) standard of encoding television signals, while Europe adopted the PAL (Phase Alternating Line) standard. The NTSC and the PAL standards provide television pictures with an aspect ratio of 4:3 (width:height), which is considered poor because people normally view scenes with a wider aspect.
In recent years, the PAL plus standard and the EDTV-2 (Enhanced Definition Television) standard have been proposed, which have a high image quality, a wide screen feature, and a compatibility with the PAL and the NTSC standards, respectively. The aspect ratios of these wide screen standards are 16:9 and 14:9, which are considerably better than the 4:3 (12:9) standard. Thus, the PAL plus and EDTV-2 standards provide viewers with superior image quality and a more realistic aspect ratio.
In both the EDTV-2 and the PAL plus standards, the higher aspect ratios are obtained by processing each screen through a 4-to-3 line decimator. Each resulting screen may be thought of as being in the shape of a letter box, as shown in FIG. 1, bordered by invalid screen portions. For example, a video signal is placed on the 360 lines at the main screen portion of the display, but not on the upper and lower 60 lines. In this manner, a flat screen with an aspect ratio of 16:9 is obtained.
In the case of the PAL plus standard, the image quality is preserved by generating a vertical resolution component known as the helper signal. As shown in FIG. 2, the helper signal for compensating the vertical resolution is multiplexed at the top and bottom, invalid portions of the letter box shape screen. In addition, a WSS signal, which signals the presence of the helper signal and which includes the aspect ratio information, is stored at invalid line 23. Reference signals, which are used to reconstruct the helper signal, are also stored in the invalid portions. A reference burst signal with a sub-carrier frequency (4.43 MHz) is disposed at the second half of the line 23. Moreover, a reference signal that represents the 100% white level is disposed on a line 623.
While the decimated screen is conveniently thought of as a letter box, each line actually comprises an analog signal. As shown in FIG. 3, line 23 is depicted as an analog signal including a blanking signal, a color burst, the WSS signal, a reference burst and another blanking signal. FIG. 4 depicts all of the lines as analog signals and distinguishes between the valid and vertical blanking intervals of the screen. It should be noted that line 23, which is located in the upper invalid portion, is considered valid according to FIG. 4 in the sense that line 23 is not in the vertical blanking interval. Line 623 is in the vertical blanking interval because line 623 carries the 100% white level, which should not be displayed.
In the case of the EDTV-2 standard, as shown in FIG. 5, VT and VH signals are multiplexed at the top and bottom of the letter box screen, and an HH signal is multiplexed at the main screen portion. The VT signal is a vertical time high band component that is lost in the interlace process when a video signal photographed in the double speed non-interlace mode is transmitted by the interlace mode. The VH signal is a vertical luminance high band component that is lost when a video signal with an aspect ratio of 16:9 is formed by decimation into the letter box shape. The HH signal is a horizontal luminance high band component with a band ranging from 4.2 MHz to 6 MHz and is frequency shifted and multiplexed to the Fukinuki hole (an area in the vertical/temporal frequency domain where the color signals are not located) of the main screen portion.
As shown in FIG. 6, NRZ signals (B1 to B4) that represent an aspect ratio are disposed on lines 22 and 285. Next, identification (ID) signals are disposed that represent whether or not signal components of VT, VH, and HH are present (the ID signals are modulated with a color sub-carrier and identify whether the signal components VT, VH, and HH are present depending upon whether the phase of the modulated signals are phase 0 or in phase with the color sub-carrier). Lastly, a 2.04 MHz confirmation signal that identifies the video signal as a signal corresponding to the EDTV-2 standard is disposed.
FIG. 7 depicts all of the lines of the screen. As discussed, only the valid screen (which includes the upper and lower invalid portions) is extracted, compressed, and encoded. Thus, data in the vertical blanking interval and the horizontal blanking interval is omitted. That is, lines 23 to 232 of a field 1 and lines 285 to 524 of a field 2 are encoded.